Occupational Health in Chilean Copper Mine Workers: A Scoping Review of Literature (2008-2019)

Introduction: the present article presents the results of a literature review on the health of mine workers on the Chilean copper market. Objective: To depict the evidence produced regarding the diseases that affect the health of Chilean mine workers. Method: A scoping review, indexed on scientific journals and other sources, for the 2008-2019 period, centered on the analysis of 20 documents that reported empirical results. Results: The main physical conditions of copper mine workers were found to be problems related to high-altitude work, the inhalation of silica dust, and noise exposure; eating and musculoskeletal disorders, cardiovascular and respiratory disorders, accidents, and low back pain. Regarding mental health conditions, the following were highlighted: psychological demands, the impact on the sleep quality due to shift work, fatigue, anxiety, depression, violence on subcontractors, and worsening of life standards after relocation, due to silicosis. Discussion: working in copper mine impacts the global health of workers, increasing the exposure to health conditions that increases the sense of suffering and worsens their quality of life.

The WHO (World Health Organization) (1) recognizes the need to develop actions that benefits the health of workers, like prevention and protection against risks and hazards, as well as promotion of workplace health. This would allow for the workers to enjoy an adequate standard of life, without the workplace diminishing it. This is achieved with healthy work environments, ones that must provide physical, psychological, social, and organizational conditions that protect and promote health and safety (2). However, there are workplaces that imply a high risk for health and safety, which leads to workers living with a sense of suffering (3).
In Chile, copper mining is a market that exposes their workers to high risks to their health. Chile accounts for the world's largest copper reserves, and it is the major exporter of this raw material. In order to accomplish the copper production cycle, thousands of workers, between direct and indirect employees, perform in this market. The evidence indicates that they expose themselves to risks and hazards to their physical health, such as, temperature variations (4), cardiovascular disturbances because of work in high-altitude (5), fractures, injuries, falls, lacerations, and musculoskeletal disorders (6), respiratory diseases, like tuberculosis or silicosis (7), exposure to polluters and toxic chemical agents (8), among others. Mental conditions include stress at work (9), caused by a shifts work system, tasks, and extensive commuting that lessens social relations and limits the emotional bond with family and friends; even so, it can affect relatives, as they witness the depressive symptoms of their partners (10). At the same time, shift work can affect the sleep-wake cycle (11); which increases the sense of distress that turns into anxiety and depression symptoms.
Due to the aforementioned, one action that can help to lessen occupational health risks and ensure more healthy surroundings in the national copper mining industry is the increase of knowledge about the group of diseases ailing the workers of this market. A contribution in this topic is this scoping review, which is the first one on the subject in Chile and Latin-America, a region where there are also other countries, such as Peru, where copper mining is important for national development. The information order and the available evidence can help as much to the stimulation of further scientific research at both the continental and national level, as well to the establishment of policies oriented at the prevention of risks and hazards in this area, something useful for directing interventions and actions that benefit the prevention of diseases and promotes safety at the workplace. The review procedure consisted of five phases (see figure 1). In the first one, articles were searched on the WOS, SCOPUS, SCIELO, PubMed, and BVS databases. These databases were considered given that they are the most used in social and health sciences areas for the publication of articles related to the subject. In this research, only English keywords were considered, which were: "health and copper workers"; "health and miners"; "occupational health and miners", "occupational risk and miners"; "safety and miners"; "health and copper mining"; "health and copper miners"; "occupational health and copper workers"; "workplace health and copper workers"; "occupational risk and copper workers"; "safety and copper workers". In all searches, the "Chile" filter was applied. In total, 402 articles that could be included in this review were found.  Furthermore, documents were searched in the virtual catalogs of the ministries and public agencies related to the subject in the country, such as the Geology and Mining Service (SERNAGEO-MIN), the Labor Directorate (DT), the Ministry of Health (MINSAL) and the Superintendence of Social Security (SUSESO). The Spanish words "mineros" and "minería" were used in these search engines. Thus, 38 documents that could be included were found.

METHODOLOGY
In the second phase, titles, abstracts, and introductions were read and then, the complete documents. Those who met the following criteria were included in the review: they reported empirical results of research about the review subject; they were published within the selected time interval (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019). This interval was chosen, as it was interesting to depict the evidence produced after the entry into force of Law No. 20.123, which regularized outsourced work in Chile, a system that has been widely questioned by copper mine workers because it poses negative impacts on occupational health and safety.
Finally, the last inclusion criteria were that they had to be primary articles written in English or Spanish, and they were published in the previously indicated databases. The exclusion criteria were related to non-empirical articles (literature reviews, theoretical and methodological), those that specialized on health in miners in industries different to copper, those that were made before the research period, those that were written in languages other than those selected, and, finally, those that they were not fully available for reading. Figure 2 summarizes the search, inclusion, and exclusion procedure for the found articles.

Figure 2. Number of included and excluded articles in this review
The documents that were included on this review are detailed on table 1. In the third phase, the documents were divided and grouped regarding their allusion to physical and mental health.
Thus, the first group was formed by the evidence related to physical conditions, while the second group by the evidence related to mental conditions (see table 2). Injuries for heavy load, vibrations, and body postures demand. Workplace harassment and anxiety in subcontracted workers.
Suspended dust Women exposed to workplace violence as they enter the copper mining industry.
Annoying noise Almost one 1/3 of workers are exposed to high psychosocial risks at work. To ensure the correct grouping, suitability was discussed. The data was extracted by the research team, paying attention to the name of the article, indexed journals or databases, year of publication, method, design, participants, and results regarding physical and/or mental health.
In the fourth phase, an analysis of the empirical evidence referred to in each registration was carried out. This allowed for the presentation of results according to the different diseases reported on both groupings.
Finally, on the fifth phase, the main results of the review were clearly stated, and then, discussed in relation to the existent literature on the subject.

Results
75% of the articles were found in scientific journals and/or web forums located in Chile. For the rest, similar percentages (5%), were found in journals from other countries, such as, the United States of America, Spain, Portugal, Korea, and Venezuela. 85% of the documents were redacted in Spanish, while the rest of them, in English (15%). The methodology that prevailed was the quantitative (80%), followed by the qualitative (10%), and mixed (10%). The research designs were mainly cross-sectional studies (50%), followed by longitudinal designs (25%), unspecified design (15%), and secondary databases review (10%). The samples were in general of good size, the study samples were mostly (60%) higher than 100 participants, highlighting a major prevalence on the male inclusion in them, taking into account that 9 out of 10 workers in Chilean mining are men. 50% of the articles were focused on the study of the workers physical conditions, whereas 45% of them were done on mental conditions. Just one document (5%) tackled the subject in both dimensions. Next, each of the studies and documents about the groupings on table 2, with the purpose of facilitating their comprehension and deepening their analysis. Objective: to evaluate the state of the right cardiac circuit, along with potentially associated metabolic variables, and distinctive responses after a long exposure to the latter condition. Method: Cross-sectional quantitative study. Participants: 120 miners who worked at an altitude of 4400-4800 meters for more than five years in 7x7 days shift work.

Frontiers in physiology
Source: own elaboration (2019). (13) found that the main diseases in surface and underground mines were sensory overload (prolonged interaction with computational or radio systems), risks of cervical sprain injuries on truck and machinery operators, the exposure to radiant temperature, which increases the cardiovascular load, and, finally, unsafe actions caused by poorly designed and distributed spaces. Workers with chronic arsenic exposure increase lymphocyte damage and decrease control of antioxidant mechanisms, increasing the risk of cancer (14).

Physical Diseases of Chilean Copper Miners Regarding physical diseases, Apud & Meyer
In another paper (15), Apud again mentioned that miners faced extreme temperatures, high workload, risks of injuries, and the development of musculoskeletal disorders. All these complications, according to the author, were because mining work implies the performance of heavy activities, such as the handling of machinery, extensive shifts, vibrations, and demanding postural loads. On the other side, it is known that Chilean mine workers are exposed to deadly and non-deadly threats (21). Considering the evidence about mining accident rates by National Service of Geology  (23). The main explanatory causes of work accidents in copper mining were referred to as the lack of protection against risks; dangerous procedures or methods, nonexistent warning signs, lack of fortification, and unplanned ground defects (24).
Research interest on chronic respiratory diseases have persisted. Thus, Galleguillos et al (25) quantified the rise of silicosis addressed in the healthcare services of Coquimbo and Santiago, pointing out that this pathology has increased the medical appointments in a 26.7%. These diseases often involve the relocation of workers to other fields, which modifies their lifestyle.
Other analyzed risks have been the alteration of eating habits and health conditions related to it. In the Solari & Solari study, it was indicated that the physical state of copper workers tends to decrease, due to the lack of physical activity and overweight, which lead to Low Back Pain Syndrome (26). In association to eating disturbances, negatives changes in habits are due to Psychoso- cial Factors, such as anxiety, lack of family support and traditions, which increments the risk of cardiovascular pathologies (27). This means that, on weekends or rest days, barbeques, alcoholic drinks, fast food, and easy preparation meals are consumed frequently (28). This also relates to higher obesity rates, diabetes mellitus, and hypertension, which, according to Zarate et al (29), were strong predictors of work absenteeism and increase healthcare expenses on the participants workers.

Mental Diseases of Chilean Copper Miners
Regarding the mental health diseases, the Vera's et al (30) study indicated that physical and cognitive fatigue corelate favorably (30). The greater the feeling of physical fatigue, the greater the feeling of cognitive fatigue; with Acute Mountain Sickness having an important weight on it. The conditions associated to these sensations were the level of job satisfaction, workload, and the shift system. Negative variations in them led to an increase in the sensation of both fatigues.
On the other hand, it has been pointed out that breaks according to day or night shifts implies an alteration in the workers sleep cycles. In the night shifts and day rest, the sleep time is shorter, as well as the latency to fall asleep is higher (31). The sleep alteration in shifts work implies the worsening of sleep quality, which difficults the reparative function itself, a worse perception in workers with 12 hours shift, given that they fail to completely attenuate their feeling of tiredness (32). The shift system, besides its influence on sleep quality, also impacts the job and family life of workers, leading to higher phycological tiredness and unsatisfaction in 12 hours shifts (32).
Sleep can be altered by altitude work, as referred to by Vera & Carrasco (33) in their study, where 44.1% of participants presented an altered oximetry, and in 55% of the cases, sleep disorders were observed, with almost 30% of total participants presenting this disease.
Meanwhile, the study by Delgado et al. (34) indicated that the relocation process implied a negative effect on general health perception and its emotional part, because the change of post cut the emotional connection with work colleagues. This was confirmed by a following study of Delgado et al (35), where it added that the waiting time before relocation is lived by workers with a feeling of uncertainty, meanwhile, after the change of field was done, the presence of sadness incremented, a negative assessment of themselves (feeling of uselessness), a lack of vitality, fatigue, and difficulties in bonding with new colleagues.
Regarding the psychosocial risks, a study done by Ansoleaga & Toro (36), in which 23% of participants showed symptoms of depression and mentioned that the high psychological demand increased by an 83% the risk of having such symptoms, while the psychological distress increased that same risk by four and a half times. As previously said, the Garrido & Hunt study (37)indicated that the effort-reward factors and the quality of the relationship with management are predictors for job strains, as subcontracted workers were exposed to higher anxiety. In this segment, the physical environment quality and the workload quantity are also predictors for unsatisfaction and work harassment. It is worth noting that violence at work is directed towards women (38), in order to chase them away. Added to it, Pérez (39) highlighted that 28.6% of men in mining, surveyed by the National Survey of Employment, Work and Health (ENETS) 2009-2010 scored high on the psychological risks at work, while a 30.4% of their female counterpart did, in the same category.
Finally, the study done by Gómez, Hernández y Méndez (40) determined that the crushing and risk prevention workers were exposed to higher psychological demands, as they were exposed to active work and to difficulties regarding the possibilities of skill development; meanwhile, operators were found to be more unsatisfied with their work.

DISCUSSION
The purpose of this study was to depict the research produced on the diseases of Chilean copper miners. For that reason, an scoping review of literature was undertaken.
The described physical health conditions of the workers are consistent with those mentioned in the national and international scientific literature on the subject. For example, workers were found at risk of developing respiratory diseases, cancer, and arsenic contact diseases, which is similar to the report on the main occupational diseases in the sector indicated in the systematic review done by Cabrera, Velásqez & Vrhovac (41) It is also consistent with findings on exposure to silica dust researchby Chen et al. (42) with Chinese mine workers. At the same time, it was found that workers are exposed to extreme temperatures, a result similar to that indicated in the narrative literature review done by Maurya et al (4).
Also, regarding the risk of accidents, entrapment, and falls of Chilean copper workers, findings are consistent with the results of the narrative review of literature (43) on mining work in India.
Finally, the evidence related to risks of musculoskeletal diseases and ergonomic risks in mining are consistent with the results of the National Survey of Employment, Work, Health and Quality of Life (44) (ENCLA), where it was noted that these alterations are recent in all Chilean economic items. That is also consistent with the results of a systematic literature review (6) of injuries and working days lost in US mines, where it was found that musculoskeletal disturbances were due to injuries, slips, and falls.
Considering the evidence found in this research about the workers mental health diseases, the results were also consistent with those reported in the national and international literature. To mention one, the evidence on anxiety, depression, and stress at work in Chilean copper workers is similar to those indicated in a study (12) conducted with Iranian copper miners.
On the other hand, the results indicated that subcontracted workers are exposed to violence at work, a fact that contributes to expanding on what Salas et al. (45) indicated: that 18% of copper mine workers recognized the existence or workplace violence. Additionally, the negative incidence in quality of life due to relocation by silicosis is also consistent with that described in a case analysis (46) of a miner from "El Teniente" in Chile.
Finally, the incidence of the shift work system on the quality of life in this review is alike to those indicated by Salinas & Roman (47), who added that women who have entered copper mining report extensive shifts as obstacles, since they put tension on the domestic and care work they perform. Simultaneously, findings that the Acute Mountain Sickness possess relations to pulmonary disease, overweight, and sleep apnea align with Penaloza (48).
Based on the above, it is possible to conclude that copper mining work affects the health of workers in different days. During the research work, it was observed that the risks and diseases hurt and degrades body attributes, leading miners to suffer effects on their health. The injuries, musculoskeletal disorders, alterations on the respiratory system impact their quality of life since they create disability and limit their possibilities for the development of new tasks and specialties. This urges us to assume that the repercussions not only refer to physical alterations; but also involve their mental health, as a physical health condition implies an increase in suffering. This is further reinforced because copper mining work implies a negative impact for the workers mental health; where the work risks and hazards end up harming them, increasing pathogenic suffering at work.
The aforesaid reinforces the need to develop effective measures to address and prevent risk work conditions in copper mining, considering that, in Chile, more than 228,000 workers are employed in that field. (24) In this sense, the recommendations contained in ILO convention 176 (49) regarding safety and health inside the mines, could be followed. Chile, unlike Peru, that ratified it in the year 2008, has not done so.
The challenge is to promote research on the physical and mental health of copper miners, allowing for a more integral comprehension of their suffering, as it is suggested in studies in the psychod-